Category Archives: Disinfection

Super chlorination is a technique used to clean and disinfect water holding vessels that cannot be washed in the traditional sense. This is different from your standard disinfection, which is for cleaning the water, not the container. Super chlorination is used when reservoirs become contininated with microorganisms or have been emptied for any reason (indicating possible esposure to contamination).

Super chlorinating is simple. On a very basic level, it is just adding a large amount of chlorine to a reservoir either as a wash applied directly to the wall or as a very strong chlorine/water solution which fills the entire reservoir.
On a more specific level, it is dependant on the strength of the hypochlorite and the amount of time the chlorine is left in direct contact with the container. The stronger the chlorine the less time required. For example, if you decide to spray the walls with straight 10% sodium hypochlorite then there is almost no time required. Whereas the normal chlorine levels in most municipal drinking water systems is not enough to ever disinfect the vessel it is in. Those low levels of chlorine will only protect the water from contamination in a reservoir that is already free of contamination.

Now you might be asking how to figure out how much chlorine to add to make super chlorinated water. If you think all you need is to dump a large amount of chlorine in then I will point out that releasing large amounts of super chlorinated water into the environment is illegal in most jurisdictions. So it is necessary to calculate how much dechlorinating agent is needed. The easiest way to know the dechlorinating needs is to measure the amount of chlorine added. In order to save money or time it is best to calculate the ammount of chlorine necessary.

50 mg/L (50 ppm) of available chlorine is a great place to start. 50 mg/L left for 24 hours will meet the best pratices and standarized procedures for most jurisdictions in North America. Below is a table outlining how much chlorine you need to add for various volumes of water.

Super Chlorination Volumes at 50 mg/L (from the City of London Port Health Authority)

From this chart you can see exactly how much chlorine to add. Add the hypochlorite solution when the system is haIf full. Then fill the tank or reservoir the rest of the way with clean water. If you are disinfecting something with plumbing, like a building or a boat, then make sure the super chlorinated water makes it to each cold water faucet by flushing until you can smell chlorine (or can measure it). Do not flush the hot water faucet. all you will do is waste chlorine and hot water.

This procedure will disinfect any reservoir. Regardless of the levels of bacterial contamination, because if it doesn’t work the first time repeat the process until it does. The most likely culprit if super chlorination doesn’t work the first time is that a pipe connected to the tank wasn’t flushed completely.

Whether you have a large tank of reserve water or your rain barrels start growing dangerous microorganisms, you may need to super chlorinate one day.

Potassium Permanganate is a very versatile chemical. It can be used for disinfection, removing hardness, removing iron and manganese. It has another health related use, it can be mixed into a paste and used as a topical salve for athlete’s foot (or similar problems). As a result potassium permanganate is a great addition to any emergency preparedness supplies.

Potassium Permaganate has the chemical formula of KMnO4, and it comes as a deep purple dry powder. This chemical is a very powerful oxidizer and it should not be stored anywhere near acids or fuel sources or it could result in fires, explosions and/or toxic gases being formed. Explosives is another use of this chemical (one which I will not be explaining here). This chemical can be stored for over a year if it is kept clean and dry and in a sealed container.

Before touching the dry powder, make sure you wear a particle mask (ideally a N95 or better). This chemical will irritate the airways if inhaled directly. Also the powder once mixed with water becomes a powerful dye. It will stain clothes permanently, stain skin temporarily and cause corrosion on any metal or masonry it touches. Anything that becomes exposed to a potassium permanganate solution becomes brown, a similar shade of brown to a henna tattoo.

To make a topical treatment with KMnO4 mix the dry powder with water until it has the consistency of playdoh. Apply the mixture on the affected area and repeat as necessary. Remember that I am not a doctor and I am not giving medical advice. I am only outlining that this chemical CAN be used for medical purposes. Whether or not you SHOULD use KMnO4 for medical applications is not something I can tell you.
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Potassium permanganate is very similar to sodium hypochlorite in the sense that they both disinfect water through oxidation. Disinfection of drinking water can be achieved by adding it to the water until the water turns pink. The pink in the water is the residual potassium permanganate. Meaning that there is nothing left to use up the chemical and any bacteria has been used. Think of the pink water as being similar to the point where you can smell bleach when using sodium hypochlorite for disinfection. Just like with the smell point of bleach has surpassed the disinfection point, you do not need to keep adding KMnO4 until you see pink. Disinfection has occurred well before you can see a lasting pink tint to the water. Using the color change is a simple and easy to remember method for disinfection of drinking water. And if the pink tint disappears at any time then you know you need to add more of the chemical to redisinfect the water.
If you want to avoid pink water and spend less money on chemicals you can buy a testing kit for manganese. Most kits can measure the residual levels of KMnO4 at levels well below the pink water threshold and well above the disinfection requirements.

For better results with disinfection it is best to filter the water through a greensand filter. Now this is not an indication of the color of the sand (it is actually black in color). Greensand is an activated filter media designed for removing iron and manganese through a process called ion exchange. The good news with a greensand KMnO4 combination is that the potassium permanganate will reactivate the filter media.

One thing to note is that potassium permanganate once added to water will make the water more corrosive. If the water is very pink it can also stain any container it is stored in. The pink water is perfectly safe to drink. I mean the water is not dangerous because of the pink coloring. It may however be dangerous for another reason or contaminant.

Another thing to note about KMnO4, is that if you add it to chlorinated water it will form a percipitate (solid). This is manganese dioxide, it is harmless except it will consume all the available chlorine in your water leaving you open to contamination from microorganisms.

With a few simple precautions KMnO4 is an excellent chemical to have on hand. It can be stored longer than sodium hypochlorite (bleach) and it can be added directly to the water unlike calcium hypochlorite. It also is very easy to see when enough of the chemical has been added. If there is a lasting pink tint that doesn’t disappear with time then the water has been disinfected.

When it comes to disinfecting your own drinking water, always be careful with the quality of chemical you use. They are not all created equal. The north american standard for chemicals used in drinking water is NSF/ANSI 60. Choose chemicals that meet this standard above ones that don’t. The will be significantly safer for your health and well being.

As with all my disinfection articles, I will remind you to always drink the safest water you can and combining treatment techniques is the best way to achieve safe drinking water

Ultraviolet light is a very popular method of disinfecting water. UV radiation is part of the electromagnetic spectrum that has incredible properties for the killing of microscopic organisms. While there are varying degrees UV resistance within microscopic organisms, not one has yet been able to develop a total resistance. Because UV disinfection systems are not chemical or biological they have an extremely long shelf life.

The Electromagnetic Spectrum with a UV Focus (From: agtuv.com)

There is a wide variety of ultraviolet disinfection systems that range from the size of a pen to large banks of meter long light bulbs and many options in between. UV systems tend to be very simple to install and operate and UV leaves nothing behind and there are no disinfection by-products from its application. In fact ultraviolet radiation can break down some potentially harmful chemicals like chlorine and chloramine compounds.

Ultraviolet Lamp (from: halmapr.com)

The limitations of UV disinfection are; distance, time, turbidity and electricity.

Proximity is critical for UV disinfection, the water needs to be very close to the UV light source. The farther away the water is the more radiation is absorbed by the water. Meaning that with increasing distance you get weakening disinfection. Proximity becomes even more critical in hard water. Hard water sources leave a white chalky residue of calcium carbonate which covers the UV light bulb, making the radiation emitted significantly weaker.

Time is another significant limitation of UV disinfection. The amount of time pathogens spend in the UV greatly affects whether or not the pathogen is neutralised. This is similar to how people get worse sunburns the longer they are exposed to the sun. Time is directly related to the flow of the water, if the flow is too much, the water will not spend enough time exposed to the radiation and will not be disinfected. Slow moving water or even static water is best.

The efficiency of UV disinfection is greatly reduced by turbidity. Turbidity physically shields the organisms from the UV light. Exactly the way a beach umbrella shades people from the sun. This is called line of sight disinfection. There is no disinfection in the shadows when using UV radiation.

Electricity is another limitation of UV disinfection systems. They are limited in two ways by electricity. First by the fact that they are quite literally light bulbs placed underwater and secondly by fluctuations in the electrical source cause fluctuations in the UV radiation field emitted from the bulbs. Both these problems are easily overcome. By sealing the system in clear waterproof chambers can effectively keep the system safe from the water. Fluctuations in the electrical source can be minimized through proper system design and using fresh/charged batteries in battery powered systems.

SteriPen Portable Ultraviolet Disinfection (from wikipedia.org)

Portability is a mixed blessing with UV disinfection systems. Smaller, pen-like devices are easy to transport, but are significantly less powerful. That means they need to be used on slower moving/still water and used for longer than larger UV systems. Another mixed blessing of ultraviolet disifection is the fact that there is no disinfection residual left in the water. Not having a disinfection residual is great if you are drinking the water immediately, otherwise recontamination can occur very quickly after the UV lamps are shut off. UV is not enough if you plan on storing the water for a long period of time.

Recirculating the water to be disinfected a second or third time will greatly increase the chances of proper disinfection. Remember that disinfection whether by UV or chlorine or any other method is one of the final stages of water treatment. Forgetting to filter the water first will make disinfection significantly more difficult. Regardless of the size of the of the system used, ultraviolet radiation can be used to supplement any water treatment process.

When camping or hiking or even during an emergency drinking water becomes very important (water is important everyday really). You can store water easily if you don’t have to travel or evacuate, but carrying enough water if you are on foot is very difficult and very heavy. There is a need for a portable, simple, effective way to make safe drinking water.

PurifiCup is a commercially available portable water solution. I had the opportunity to test one and I put it up against some laboratory tests and my own personal judgments. It is very simple to use and is compact enough to fit into any bag and most cup holders.
This filter fits perfectly over wide mouth Nalgene bottles and screws directly onto standard water bottles. This product is very versatile and that makes it useful in a wide variety of situations.

PurifiCup Natural Water Purifier over a Nalgene Water Bottle

Some useful statistics on the PurifiCup. The cup is 10 fl oz, and it can filter 100 to 150 cups before it needs a new cartridge. It is 7.3 cm in diameter and 16 cm in height. The filter media includes ion exchange resins, activated carbon and nanoscale silver coating membrane. The PurifiCup retails for $59.99 for the cup and filter, and replacement filters costing $13.99

Normal filters treat water by physically removing suspended materials in the water. A good physical filter removes particles as small as 0.2 microns. This will make the filter capable of removing all sizes of bacteria (but not all viruses).

The PurifiCup however isn’t a normal filter. It for one doesn’t filter below the 1.0 micron level. That is not rearly fine enough to remove all types of bacteria. This may seem like a bad thing, but the Purificup does something that no other portable water filter does (that I am aware of). The PurifiCup disinfects as it filters the water with a nano-silver membrane. Nano-silver has been shown to kill over 600 different types of bacteria.

What I wanted to know was, in a real world setting does it work? Does the product come close to meeting the claims? I tested the PurifiCup’s ability to remove turbidity, chlorine, color and its ability to kill bacteria.

PurifiCup Packed Up For Storage Or Travel

I took a sample of treated water to measure chlorine removal. The water sample I chose here is typical municipal drinking water. I also took a sample from a nearby river. This river represents a typical backup water source that could be used while hiking or in a survival situation.

There was a chlorine residual of 2.03 mg/L to start with. After filtering with the PurifiCup chlorine was reduced to 0.16 mg/L. To put it simpler, there was a 97% reduction of chlorine in the tap water. That level or chlorine reduction is amazing.

In the river sample I tested trubidity and color. Turbidity is the measure of suspended particles in the water, or the measure of the cloudiness of the water. Color is the measure of clarity of water, how close to perfectly clear is the water separate from suspended particles.
(Science Note: turbidity measures the scatter of light through the water sample and color measures the absorption of light by the sample). If you think of loose leaf tea, turbidity is the leaves in the water and color is the brown tint the water takes on. In general the lower the turbidity an the lower the color the safer the water is to drink (this is NOT always true).

The river sample started with 18.4 NTU (Nepheletic Turbidity Units) and after filtration it was 4.72 NTU. To put a little perspective to these numbers anything under 5NTU is invisible to the naked eye and at my water system I am not allowed to go over 1NTU. There was a 75% reduction in turbidity. The remaining turbidity is not terribly impressive but expected from a filter of 1.0 micron. Remember, the PurifiCup doesn’t claim to physically remove everything from the water.

Color is the final parameter I tested. Color isn’t in itself a health related property of water. A lot of color doesn’t necessarily mean the water is unsafe to drink. Removal of color however is a good indicator of the removal of many dissolved chemicals. The Color of my river sample was 128 (there are no units for color). The PurifiCup reduced that number to 81. Therefore 63% of the color was removed. This may not seem like a lot, but color is one of the most difficult things to remove from water.

Now for the parameter I was most curious about on a professional and personal level. Bacteria; does the PurifiCup actually disinfect water? I had to send this to an external environmental laboratory as I don’t have access to a biological lab. This limited the number and types of bacteria I tested. I chose to test for heterotrophic bacteria (heterotrophic plate count or HPC). These bacteria are not pathogenic, but they are resistant to many treatment processes and that makes them an excellent indicator of treatment success. I tested the HPC of the river and PurifiCup effluent.
First, bacteria tests are measured in colony forming units (cfu). A cfu is a group of bacteria that group into a visible blob (colony) of bacteria. The raw water from the river had a cfu count of 800 and the treated water had a cfu count of 500. 500 may seem like a lot, but it is a misleading number. Remember the disinfection doesn’t mean the killing of all bacteria, that’s sterilization. Disinfection is the removal or inactivation of pathogenic bacteria. Inactivation stops the ability of bacteria to reproduce and cause disease. Like I said before 500 cfu may seem like a lot. But these 500 cfu were inactivated. Remember the 1micron filter? A lot of bacteria go through the filter, but unlike the raw sample the 500 cfu didn’t grow. So while 500 cfu is a big number, they are not able to cause disease. The PurifiCup made the sample significantly safer to drink.

I highly recommend this product as part of a water purification system. The portability and low cost of the PurifiCup makes this product a simple addition to your emergency preparations or for an avid outdoors-man’s kit.

Storing water in case of an emergency is a good idea. Having a reserve enables people to weather emergencies and minor service disruptions. A backup source of water is essential for emergency preparedness, three days without water will lead to death from dehydration, but serious and lifelong complications can occur well before you die from dehydration. Did you know that water sometimes needs to be retreated because clean water becomes contaminated? Water typically gets re-contaminated as people use water and they aren’t careful enough to prevent re-contamination, think about when you are washing up, hands are dirty and that leads to contamination of your stored water. Also a lot of stored water is stored for a long time “in case of emergency”. The problem with long term storage is the disinfectant residual deteriorates with time, reducing the water’s ability to prevent bacterial growth.

Preventing contamination is easier than removing contamination. Leave your stored water is a sealed and preferably airtight container. This physical barrier will stop bacteria in the environment from coming into contact with your drinking water. Next is to only open your reservoir with clean hands. Preferably washed with soap and water. It is better to pour the water you need for clean up before you make a mess. This is actually very important when you go to the bathroom, microscopic pieces of fecal matter on your hands will transfer to everything you touch, including the spigot/lid of your reservoir. Bacteria in that fecal matter will travel up the spigot into the water, it will only be a matter of time. Clean hands and routinely cleaning the exterior of your water storage tank/bottle/container/reservoir are essential to prevent contamination.